The reason that Artifactory appends ".marker" to the Docker layers and why it's an expected behavior that can save storage and network bandwidth.
Affects all versions till 6.9.2
When the Docker client downloads from a remote Docker repository, it does not download the entire image at once, it downloads it, layer by layer (including the manifest).
In case the Docker client already has a particular layer, it will not attempt to download the layer and Artifactory will not request it from the upstream (Docker Registry).
The marker layers will be created to indicate that there is a layer that is part of an image which already exists in the docker client, but the layer has not (yet) been requested from Artifactory.
For that reason, Artifactory has not requested it from the upstream.
If the marker layer "SHA-256” file is downloaded, it will only include “marker” ( to save bandwidth and storage).